Microwave detection apparatus for locating cancerous tumors particularly breast tumors

ABSTRACT

Microwave tumor detection apparatus includes a probe having a working end arranged to contact tissue. Positioned in the probe is a plurality of rectangular waveguides arranged in columns and rows such that each waveguide has an aperture at the working end of the probe that is oriented substantially perpendicular to the aperture of the waveguide in any adjacent column and row of the array. The waveguides constitute antennas tuned to receive microwave radiation emitted by the tissue opposite the working end of the probe. The waveguides are coupled electrically and mechanically to dedicated radiometers in the probe for detecting the temperatures of tissue opposite the waveguides. These radiometers have thermally conductive casings which are mounted to a common heat sink and are insulated so that all of the radiometers have a uniform thermal distribution. Also, a thin thermally insulating interface pad may be located between the working end of the probe and the tissue contacted by the probe to prevent such contact from causing changes in the surface temperature of the tissue. A method of detecting breast tumors is also disclosed.

RELATED APPLICATION

This application is a division of Ser. No. 08/627,117, filed Apr, 3,1996, now U.S. Pat. No. 5,662,110.

This invention relates to microwave detection apparatus. It relatesespecially to such apparatus suitable for screening for breast tumors.

BACKGROUND OF THE INVENTION

According to the American Cancer Society, approximately 180,000 Americanwomen were diagnosed with breast cancer in 1993. Approximately 45,400died from the disease. In the United States, breast cancer continues tobe the most common of the nonpreventable cancers diagnosed among women.Much of the urgency in improving early diagnosis of breast cancer stemsfrom the tragic and steady rise in the incidence of same. . . . 1 in 16women in 1962, to 1 in 9 women in 1993. In fact, the incidences ofbreast cancer have been increasing steadily in the United States sinceformal tracking of cases through registries began in 1930. There hasbeen no appreciable change in the death rate during the same period.

It has long been known that early detection of malignant tumorsincreases the chance of survival. In fact, the results of a 1976National Institute of Heath Survey indicate a dramatic increase insurvival (from 56% to 85%) as a result of early detection.

The technique that is used most often to screen for breast tumors ismammography. However, mammography exposes the patient to x-rays. Thisinvolves some hazard even though the radiation dosages are relativelysmall because multiple exposures of each breast are required in order tocover all quadrants of the breasts. Also, the procedure can be somewhattime consuming because the technician taking the mammogram is requiredto position the apparatus prior to taking each picture and then takerefuge behind a leaded window while the x-ray tube is operative to avoidundo exposure to the radiation. Most importantly, mammography isdisadvantaged because when adjusting the apparatus to the patient inorder to obtain enough compression of the breast to ensure adequatex-ray penetration, the working end of the apparatus is often positionedso that the x-rays fail to properly illuminate the upper half of thebreast and the axillary gland area above the upper outer quadrant of thebreast where most tumors originate. This is particularly so forindividuals with small breasts. Indeed, studies have shown that 80% ofall breast tumors occur in the upper half of the breast and fully 69%arise in the upper outer quadrant of the breast and the axillary glandarea. Resultantly, mammography misses many tumors.

Another technique for measuring tumors is thermography. Thermographyrelies on the fact that tumors tend to have higher temperatures thannormal tissue due to the higher metabolic activity and vascularity oftumors. Therefore, the tumors tend to appear as hot spots in athermogram of the breast. Thermography has definite advantages overmammography because it is non-invasive and non-hazardous both to thepatients and to the personnel taking the thermograms.

The most common type of thermography is infrared thermography.Diagnostic techniques using electromagnetic emission in the infraredregion of the spectrum have been available for many years and haveproved useful in measuring surface temperature distributions in thebody. However, body tissue rapidly absorbs electromagnetic energy at theinfrared frequencies. Since the heat associated with a subcutaneoustumor is transferred by radiation as well as convection and conduction,the thermal pattern seen at the skin surface due to such a tumor can bealtered significantly. In fact, in some cases, a relatively deep tumormay not appear at all in an infrared thermogram of the affected area.Thus, infrared thermography is essentially limited to surfacemeasurements which can vary greatly in response to external factors suchas physical activity, menstrual cycle, substance intake, etc.

More recently there has been developed thermography systems for locatingtumors in the body using microwave radiometry. These systems, whichoperate at the lower microwave frequencies, provide improvedtransmission characteristics in tissue and, therefore, allow detectionat greater depths in tissue. Two such systems for detecting canceroustumors are described in my U.S. Pat. Nos. 4,346,716 and 4,774,961. Bothof these systems screen for tumors by detecting radiometrically theincreased energy emitted in the microwave band by the relatively hotcancerous tumors. The system described in the former patent utilizes asingle relatively small detection antenna. Therefore, it is impracticalfor use in screening for breast tumors because it takes too long toprobe all quadrants of the breast. The microwave detection apparatusdescribed in the latter patent avoids this problem to some extent byemploying a detection antenna array composed of a relatively largenumber (i.e., 6-12) of individual antennas which are switched, in turn,to a single radiometer. This allows the apparatus to image the entirebreast, or at least a large area thereof, with each positioning of theapparatus relative to the breast.

When screening for breast tumors using the microwave radiometry systemin my '961 patent, the usual procedure is to compare the temperatures atcommon locations on the two breasts of the patient to determine if thereis a temperature difference. In other words, absent tumors, there is asurprising correspondence of temperatures at corresponding locations onopposite sides of a given individual, i.e., a temperature differentialwithin about 0.2° C. Consequently, if a larger temperature differentialdoes exist at corresponding locations on the two breasts, this is anindication that an abnormality may be present in the breast with thehigher temperature reading. The usual practice, then, is to taketemperature readings at various locations on one entire breast and thenreposition the apparatus to take similar measurements at correspondinglocations on the other entire breast. These readings are fed to acontroller with data processing capability which compares them in orderto produce a thermogram or other visual display showing the temperaturedifferentials at the corresponding locations on the two breasts. Usuallyalso, the temperature-indicating signals are processed using variousknown averaging, enhancement and target recognition techniques toincrease the probability that a tumor-indicating hot spot will berecognized in the display.

When scanning for breast tumors using a multiple-antenna array accordingto the above procedure, it must be taken into consideration that anindividual's breasts are handed. In other words, when facing anindividual, the axillary gland area of the individual's right breast isto the left of the observer, while the axillary gland area of theindividual's left breast is to the right of the observer. Therefore, ifan antenna array is positioned against that individual's right breast,the antenna in the upper left corner of the array will be closest to thegland area of that breast. On the other hand, if the same array ispressed against that individual's left breast, the antenna in the upperright corner of the array will be closest to the gland area of thatbreast. This means that when temperature measurements are being taken ofboth breasts, the temperature information from the various antennas inthe array being fed to the system controller must be switched so thatproper comparisons are made of common points on the two breasts.

The multiple antenna arrangement described in my '961 patent isdisadvantaged in that it requires breast compression so as to reduce thetissue thickness being examined in order to obtain accurate tissuetemperature measurements of the breasts. In one embodiment of thatpatented system, a single multiple antenna array is held against thebreast in order to compress the breast. In a second embodiment of thatsystem, the breast is compressed between a pair of opposed multipleantenna arrays. In both cases, it has proven difficult to obtain therequired intimate contacts between all of the antennas in the antennaarray(s) and the surface of the breast for all areas of the breasts,with the result that some tumors may go undetected.

Also, when screening for tumors in relatively small breasts, in order toadequately compress the breast with the antenna array, the upper arrayhas to be positioned so that, like the prior mammography systemsdescribed above, it may fail to detect tumors in the upper half of thebreast and the axillary gland area above the breast.

Another disadvantage of having to compress the breast in order to screenfor tumors is that the very act of compression upsets the bloodcirculation in the breast tissue and causes temperature changes therein.Therefore, after the antenna array(s) has been pressed against thebreast, it is necessary to wait a couple of minutes to allow the breasttemperature to stabilize before taking temperature measurements. Thisobviously increases the overall breast examination time. Also, themaintenance of the breast under compression causes discomfort to somepatients and makes them more reluctant to undergo the breast screeningprocedure.

Further, in the prior multiple antenna detection systems describedabove, the individual antennas are arrayed in a stack or in offsetcourses like bricks in a wall. Resultantly, the array has a relativelylarge footprint or there may be gaps between the antenna patterns of thearray which may allow some tumor-indicating hot spots to be missedduring the breast examination.

Finally, the use of a multiple antenna array time-shared with a singleradiometer introduces switching artifacts into the signals from theradiometer which can degrade the temperature readings obtained by theprior system.

For all of the above reasons, microwave radiometry is not as widely usedto screen for breast tumors as might be expected considering theadvantages which it offers in terms of detection penetration depth,safety and efficiency.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provideimproved microwave radiometry apparatus for detecting tumors,particularly malignant breast tumors.

Another object of the invention is to provide such apparatus whichfacilitates making temperature comparisons at corresponding locations ona patient's two breasts.

Yet another object of the invention is to provide microwave detectionapparatus which can screen for breast tumors in a minimum amount oftime.

A further object of the invention is to provide apparatus of thisgeneral type which does not require compression of the breast during abreast examination.

Still another object of the invention is to provide microwave radiometryapparatus for screening for breast tumors which does not materiallyalter breast temperature during the screening process.

A further object of the invention is to provide apparatus of this typewhich includes a relatively small, hand-held, multiple antenna probewhich can be positioned in intimate contact with all areas of the breastso as to accurately detect the temperatures thereat.

Other objects will, in part, be obvious and will, in part, appearhereinafter. The invention accordingly comprises the features ofconstruction, combination of elements and arrangement of parts whichwill be exemplified in the following detailed description, and the scopeof the invention will be indicated in the claims.

In general, my detection apparatus includes a hand-held probe which maybe positioned so that the working end of the probe makes intimatecontact with a relatively large area of a patient's breast. Exposed atthe working end of the probe is a compact array of microwave-receivingantennas which detects the electromagnetic energy in the microwaveregion emitted from the tissue contacted by the probe. Each antennaincludes a short section of rectangular waveguide, preferably dielectricloaded, which is coupled both mechanically and electrically directly toa dedicated radiometer also present in the probe. Thus, the temperaturemeasurements for all antennas in the array are taken simultaneously.

The waveguide-radiometer pairs are oriented about the probe axis so thatthe end apertures of the waveguides are arranged in contiguous columnsand rows at the working end of the probe and such that the aperture ofeach waveguide is oriented 90° relative to the aperture of any adjacentwaveguide in the array. This produces an array which may be brought intocontact with an appreciable area of the breast and yet one which hasminimal gaps between the antenna patterns of the various antennas in thearray. Resultantly, the probe, with each positioning, can obtainaccurate temperature measurements, with a reasonable degree ofresolution, from a relatively large continuous area of the breast sothat an entire breast can be examined with minimum repositionings of theprobe.

Preferably, all of the radiometers in the probe are mounted to a commonthermally conductive fixture so that the radiometers make intimatethermal contact in exactly the same way with the fixture over relativelylarge surface areas so that there is a very uniform thermal distributionbetween the radiometers. The fixture thus functions as a heat sink tomaintain all of the radiometers at substantially the same temperaturethereby stabilizing their gains assuring that they will take accuratetemperature readings which will remain consistent over time. To furtherassure their stability, the radiometers are thermally insulated so theywill not be affected by changes in the ambient temperature.

The temperature-indicating output signals from the radiometers, whichcomprise the output from the probe as a whole, are applied to acontroller which processes the signals to produce digital datarepresenting the temperatures of the areas of the breasts contacted bythe probe. This data is used to control a monitor which may display theactual or relative temperatures at corresponding areas of the patient'sbreasts. The display may be in the form of a thermogram or some othertemperature-indicating presentation such as one which color codes thedifferent temperatures. In any event, the display will pinpoint thelocations of any subcutaneous hot spots in the breasts that may beindicative of malignant tumors at those locations.

When screening for breast tumors with my apparatus, the procedure usedis quite different from that described in my above-referenced '961patent. Here, the patient is examined while lying supine on anexamination table with the arms by the side with the hand on the hips toavoid the trapping of air at the breast areas. Then, using the probe,temperature measurements are taken at corresponding locations on the twobreasts one right after the other. In other words, the working end ofthe probe may be placed over a selected location on the left breast andthe microwave energy emitted thereat is received by each antenna in theprobe and measured by the corresponding radiometer. The temperatureinformation from each radiometer may then be stored in the controllerand displayed if desired. Then, the examiner may position the probe atthe corresponding location on the right breast and the temperatures atthat location measured and stored in the same fashion. The apparatuscontroller may process the information using various averaging andsignal recognition techniques to provide a temperature comparison of thetwo common breast locations. The examiner may then probe additionalcommon areas of the two breasts one after the other in the same fashion.It is important to note that the probe is dimensioned so that itsantennas can make intimate thermal contact with all breast sitesappropriate for examination including upper half of the breast and theaxillary gland area, even for those with small breasts.

When both breasts have been thermally mapped in their entireties, theexaminer may cause the controller to store all the readings on a tape ordisk so that the examination results for a given patient will beavailable for comparison with the results of a subsequent similarexamination of that same patient.

An obvious advantage of this procedure is that the correspondingtemperature measurements for the two breasts can be taken very closetogether in time thereby minimizing the chances of extraneous factorseffecting the temperature measurements. More importantly, the examinercan obtain more information by making the temperature comparisons foreach breast location substantially immediately. For example, theexaminer may notice a slight temperature differential at correspondinglocations on the two breasts which may provoke him or her to probecertain closely adjacent common locations on the two breasts to see ifthe temperature difference is greater or less at the latter commonlocation. Following such "clues," the examiner may home in on a hot spotin one of the breasts. This would be impossible to do with the priormultiple antenna detection systems described above which taketemperature measurements of the breast entireties before making anytemperature comparisons.

As noted above, the placement of a probe against the skin can itselfcause changes in the skin temperature thereby upsetting the radiometrictemperature measurements. To avoid this problem, my apparatus mayinclude an interface pad of low thermal mass between the working end ofthe probe and the skin area to be contacted. While the pad may be placedon the working end of the probe, it is more preferably a thin, mildlyadherent insulating sheet placed over each of the patient's breastswhich help to stabilize the breast surface temperature. As will bedescribed in more detail later, these sheets may be marked with grids tofacilitate proper placement of the probe at common locations on the twobreasts to make the temperature comparisons described above.

Thus, using the present apparatus, one should be able to screen anindividual for breasts tumors in no more time that it takes for astandard mammography examination. Furthermore with my apparatus, allareas of the breasts may be examined with equal facility therebyminimizing the likelihood that a subcutaneous tumor will be missedduring the examination.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a fragmentary perspective view of microwave detectionapparatus incorporating the invention being used to give a breastexamination to a patient;

FIG. 2 is a perspective view on a much larger scale showing theradiometric probe component of the FIG. 1 apparatus;

FIG. 3 is a sectional view on a still larger scale of the probe depictedin FIG. 2;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3;

FIG. 5 is an end view of the FIG. 3 probe showing the receive patternsof the probe's antenna array, and

FIG. 6 is a plan view on a larger scale showing the interface pads thatmay be used with the FIG. 1 apparatus, which view also illustrates theuse of that apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 of the drawings, my apparatus, shown generally at10, is being used to conduct a breast examination of a patient Preposing in a supine position on an examination table T. The apparatus10 includes a roll stand or wall bracket 12 which supports a verticallyadjustable arm 12a that is arranged overhang table T. Suspended from arm12a is a radiometric probe 14 having a working end 14a and which iselectrically connected by an extensible cable 16 to a controller 18having a control panel 18a. Controller 18 may be positioned on aplatform 12b also supported by stand or bracket 12.

When the probe working end 14a is placed against the patient's breastB_(l), or B_(r), the probe will detect the thermo-radiation emitted bythe contacted breast area and emit corresponding electrical signals viacable 16 to controller 18. The controller may then cause a monitor 22,also supported by platform 12b, to provide a visual indication of thesensed temperatures. When the examiner is satisfied with the position ofthe probe, a control device such as a control button 24 on probe 14 maybe depressed which sends a signal to the controller which causes thecontroller to store the temperature readings in a memory unit in thecontroller. Another control device such as a two-position switch 25 onprobe 14 is present to allow the operator to tell the controller whichbreast is being probed to account for the fact that the breasts arehanded as described above. Of course, the controls 24 and 25 could justas well be foot pedal switches or buttons on control panel 18a.

If desired, known means may be provided for counterbalancing probe 14.In the illustrated apparatus 10, these means comprise a coil spring 26stretched between arm 12a and the probe 14. They could just as well be apulley/counterweight arrangement in arm 12a. The counterbalance helps tominimize arm fatigue when an examiner has to manipulate the probe 14 fora prolonged period.

Also, thermally insulating interface pads 30_(l) and 30_(r) to bedescribed in more detail later, may be present between the probe workingend 14a and the, breasts B_(l) , B_(r) to stabilize the breasttemperature and to prevent breast surface temperature change due tocontact by the probe.

Referring now to FIGS. 2 to 4 of the drawings, probe 14 comprises agenerally cylindrical housing 32 preferably made of a suitable strong,impact resistant, electrically insulating plastic material. One end ofhousing 32 is closed by an end wall 32a; the other end of the housing isopen. Also, a segment of the housing adjacent to end wall 32a may have areduced internal diameter thereby forming an internal shelf 36 spacedfrom end wall 32a for reasons that will become apparent.

Housing 32 is designed to contain an array of substantially identicalradiometric detection assemblies shown generally at 38. The illustratedprobe 14 has four such assemblies. Each assembly comprises a generallyrectangular radiometer 42 having a thermally conductive outer casing 42aand a coupling probe 42b extending from the outer end of the casing.Each assembly also includes an antenna in the form of a section ofrectangular waveguide 44 telescoped onto, or otherwise connected to, theouter end of the radiometer so that the waveguide is coupled to theradiometer both mechanically and electrically via the former's couplingprobe 42b.

The radiometer 42 of each assembly 38 is mounted directly to anelongated fixture 46 made of a thermally conductive material such asaluminum or copper metal. As shown in FIG. 3, fixture 46 is somewhatlonger than radiometers 42 and, as seen in FIG. 4, it has a plurality,herein four, fins or blades 46a which extend out at right angles to oneanother. The fixture 46 supports each radiometer 42 such that allradiometer casings 42a are in intimate thermal engagement in exactly thesame way with fixture 46 over large portions of the casings' surfaceareas. In other words, one broad wall of each casing 42a is opposite anarrow wall of an adjacent casing at all wall areas. This achieves avery uniform thermal distribution between the radiometers. Furthermore,for reasons that will become apparent, the fixture orients the detectionassemblies 38 as a whole so that their waveguides 44 are arranged incontiguous columns and rows with the end aperture 44a of each waveguidebeing substantially perpendicular to and more or less bisecting theaperture of any adjacent waveguide 44 in the array.

As noted previously, fixture 46 may be somewhat longer than radiometers42 so that it projects beyond the radiometers toward the housing endwall 32a. Its inner is keyed into slots 52a in discoid bracket 52 whichis arranged to seat on the internal shelf 36 of housing 32 so as to fixthe positions of the inner ends of assemblies 38.

Each radiometer 42 has a multi-conductor cable 42 extending from theinner end of the radiometer. These cables are gathered together and passthrough a grommet 54 mounted in the housing end wall 32a to become theprobe's external cable 16. Also, the control buttons 24 and 25 havewires 24a and 25a which pass through grommet 54 into cable 16.

In order to thermally isolate the detection assemblies 38 from theenvironment, the remaining space inside housing 32 is preferably filledwith a thermally insulating material 56 such as closed cell foam.

Referring now to FIGS. 2 and 3, the open end of housing 32 is closed byan end plate 58 which may be of the same material as housing 32. Plate58 has an array of four contiguous rectangular openings 62 for snuglyreceiving the outer ends of the four waveguides 44, thereby fixing thepositions of the outer ends of the detection assemblies 38. Thus, theend plate 58 defines the working end 14a of probe 14.

The radiometer 42 comprising each detection assembly 38 is preferably ofthe Dicke switch-type. This radiometer design reduces the effects ofshort term gain fluctuations in the radiometer. The output of theradiometer is proportional to the temperature difference between theassociated waveguide 44 and a reference load in the radiometer. Thedesign and operation of the radiometer is described in detail in myabove U.S. Pat. No. 4,744,961, the contents of which are herebyincorporated herein by reference. A radiometer of this design suitablefor use in apparatus 10 is available from Microwave Medical Systems,Inc., Acton, Mass.

Since the radiometer per se does not constitute part of the presentinvention, it will not be detailed herein. Suffice to say that theradiometer has a bandwidth of about 500 MHz centered at 4.0 GHz. In use,the radiometer is maintained on standby so that it is heated by itsinternal elements to a temperature of about 34° C. But since all theradiometers are mounted to a common heat sink as noted above, they areall maintained at essentially the same temperature. Each radiometer hasdimensions of about 10.2×3.8×1.5 cm. and each device weighs about 3 oz.so that an array of four detection assemblies 38 can be contained withina probe housing 32 that is in the order of 5.7 cm in diameter and 1.5 cmlong, with the overall probe weighing under 20 oz. Thus, an examiner caneasily manipulate the probe by hand when examining a patient.

Referring to FIG. 3 of the drawings, the waveguide 44 of each detectionassembly 38 may be about 2.54 cm long and have a simple TE₁₀ -modeaperture 44a designed to be in direct contact with the emitting surface,e.g., the surface of a breast B_(l) or B_(r) (FIG. 1). For dielectricloading purposes to reduce the physical size of the waveguide aperture44a, a slab 64 of non-magnetic dielectric material may be located ineach waveguide 44. A low-loss dielectric having a relative dielectricconstant of about 9, e.g., aluminum oxide ceramic, may be employed,thereby providing an aperture size of about 3.10×1.55 cm. This apertureis slightly larger than the wavelength of the tissue contacted by theprobe (e.g., about 3 cm at 4.0 GHz) which optimizes the antenna'sdetection penetration depth in the tissue.

In other words, when the aperture is matched to the tissue beingcontacted by the probe 14 as described, the antenna has maximumdirectivity and obtains maximum spatial resolution and tissuepenetration. Furthermore, the tissue-air interface reflection at eachantenna is minimized thereby providing maximum coupling of the emittedsignal to the associated radiometer. Yet, an aperture of this sizeresults in an antenna array which can still receive emissions from anacceptably large area of the breast with a single positioning of theprobe 14. In other words, the above described antenna array of fourorthogonal waveguides produces a nice balance between the array'scoverage on the tissue and its ability to penetrate the tissue withminimal gaps between the antenna patterns of the antenna array.

This is illustrated in FIG. 5 which shows the roots of the antennapatterns A for the four waveguides 44 of probe 14. Each pattern has thegeneral shape of a frustum of a cone whose diameter becomesprogressively smaller with increasing distance from the aperature 44a ofthe associated waveguide. As seen from FIG. 5, the maximum diameters ofthe patterns A correspond to the widths of waveguides 44. Resultantly,the patterns of adjacent waveguides overlap and afford very uniformcoverage of the tissue contacted by the working end 14a of probe 14.

As best seen in FIGS. 2 and 3, the outer surface 64a of each dielectricslab 64 is preferably domed so that it projects out slightly beyond theend plate 58. Thus, when the working end 14a of the probe is placedagainst a patient's breast during an examination, there will be no airpockets present between the ends of the waveguides 44 and the patient'sskin that could degrade the temperature measurements taken by probe 14.

Refer now to FIG. 6 which illustrates the interface pads 30_(r) and30_(l) in greater detail. Each pad is basically a thin (e.g. 0.12 cm)sheet of a thermally insulating material such as closed cell foam. Thepads are sized to cover the breasts B_(r) and B_(l) and the areas aroundthe breasts including the axillary gland areas AG_(r) and AG_(l). Thepads ³⁰ r, 30_(l) may be contoured to some extent so that they conformmore or less to the shape of the breast and preferably their undersidesare covered with a release adhesive so that the pads may be mildlyadhered to a patient's chest as shown in FIG. 1. When so applied, theinterface pads insulate the breast areas from the atmosphere so thattheir surface temperatures are stabilized. Also, when the probe 14 isplaced against a breast during an examination, the overlying padisolates that breast so that contact by the probe 14 does not alter thesurface temperature of the contacted area of the breast. Therefore, itis not necessary to wait at all before a temperature reading can betaken at that breast area.

Preferably also, the pads 30_(r) and 30_(l) carry grids 70_(r) and70_(l) respectively, to facilitate targeting selected areas of theunderlying breasts. As illustrated in FIG. 6, each grid may includelettered columns and numbered rows of lines. Preferably, the grids aremirror images of one another so that common points on the two breastsmay be designated by the same letter and number on the two grids. Thus,when comparing the temperatures at corresponding locations on the twobreasts using probe 14, the working end 14a of the probe may bepositioned opposite a selected lettered column and numbered row of eachgrid. To facilitate such placement, benchmarks 72 may be inscribed 90°apart on the probe housing 32 adjacent to the working end of the probeas shown in FIG. 2. Thus, when examining a patient, the examiner mayline up the bench marks 72 with the grid lines on the two interface pads30_(r), 30_(l) which will ensure that common locations on the twobreasts are being probed as the temperature comparisons are beingdeveloped.

Instead of using the interface pads 30_(l) and 30_(r), a singleinterface pad may be affixed to the working end 14a of probe 14 as shownin phantom at 74 in FIG. 3. Pad 74 would also serve to insulate thecontacted area of the breast from the probe. However, the pad 74 wouldobviously not help to stabilize the surface temperatures of the breastsas do pads 30_(l), 30_(r),

When examining a patient P (FIG. 1), the examiner might start bypositioning probe 14 at location B1 of pad 30_(r) as shown in FIG. 6,after setting switch 25 to its "right" position so that the controller18 knows that the right breast is being probed. When the examiner issatisfied with the position of the probe, the control button 24 may bedepressed so that the signals from the four radiometers 42 representingthe temperatures at the breast areas contacted by the four antennas 44are logged into the controller's memory.

Then, after setting switch 25 to its "left" position, the examiner mayplace probe 14 opposite the corresponding area B1 on the left breastand, by depressing switch 24, store the four temperature readings fromthat location in the controller 18 in the same way. The controllerprocesses the temperature data at the two locations and the temperaturesmay be displayed by the monitor 22. The visual presentation may beactual temperature numbers overlaid on a visual display such as FIG. 6.Alternatively, the different temperatures may be displayed in differentcolors by the monitor 22. Also, controller 18 may be programmed to usevarious known signal recognition and enhancement techniques so that whenone of the detection assemblies 38 in probe 14 detects an area of thebreast that is significantly hotter than the breast areas under theother three assemblies 38 of the probe, an enhanced output from that oneassembly 38 will readily be apparent in the monitor display. In theexample in FIG. 6, the average temperatures detected at locations B1 onthe two breasts are displayed and shown as 36.1° C. and 36.0° C.,respectively. Therefore, the first temperature comparison shows no hotspot.

The examiner may then move the probe 14 to a second location on theright breast, say, to the position C2, and log the four temperaturereadings at that location into the controller 18, i.e., averagetemperature 36.1° C. The examiner then places the probe 14 opposite thecorresponding location C2 on the left breast and the four temperaturesat that location are detected by the assemblies 38 and logged into thecontroller. At that location, apparatus 10 detects an elevated averagetemperature of 36.6° C. indicating that a tumor may exist in the leftbreast B_(l) near that location. The examiner may then probe othercommon areas of the two breasts, such as location E2, to develop othertemperature comparisons. Following sucessive comparisons, the examinerwill be able to home in on the location of the tumor T at position D3 onthe left breast.

The controller 18 can also process the signals from probe 14 in otherways such as by comparing the temperature detected by each probeassembly 38 with the average of the temperatures detected by the otherthree assemblies to avoid the effect of cold spots in the temperaturemeasurements. Further, the patient may be given a vasoconstrictor, suchas phenylephrine hydrochloride, so that a hot spot due to a tumor willstand out against the temperature of normal tissue. This is possiblebecause the vasoconstrictor tends to reduce the temperature of thetissue surrounding a tumor but not the tumor itself due to the fact thata tumor has its own vasculature which is relatively unaffected by thevasoconstrictor.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description are efficiently attained. Also,certain changes may be made in the above construction without departingfrom the scope of the invention. For example, the apparatus may be usedto probe for subcutaneous malignant lesions other than breast tumors.Also, in some cases, the radiometers 42 may be in direct heat exchangecontact thereby avoiding the need for fixture 42. In that event, theapparatus will still have many of the advantages described above.Therefore, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the inventiondescribed herein.

What is claimed is:
 1. A method of detecting breast tumors in anindividual having two breasts, said method comprising the steps ofpositioning an array of microwave antennas against a selected area ofone of said breasts so as to receive electromagnetic emissions from aplurality of substantially contiguous subcutaneous locations in said onebreast;simultaneously detecting said emissions to produce acorresponding first plurality of electrical signals indicative of thetemperatures of said locations; digitizing and storing said firstplurality of signals; immediately positioning said antenna array againstthe corresponding area of the other of said breasts so as to receivesimilar emissions from corresponding subcutaneous locations in the otherbreast; simultaneously detecting said emissions to produce acorresponding second plurality of electrical signals indicative of thetemperatures at said locations in said other breast; digitizing andstoring the second plurality of signals; comparing said first and secondpluralities of signals to determine if the detected temperatures fromcorresponding locations in the breasts differ by more than a selectedamount, and locating a thermally insulating interface pad between theantenna array and each breast before positioning the antenna arrayagainst each breast.
 2. The method defined in claim 1 and including theadditional step of inscribing a grid on the interface pad to facilitatepositioning the antenna array against each breast.
 3. A method ofdetecting breast tumors in an individual having two breasts, said methodcomprising the steps of:forming a probe having a working end forcontacting tissue and a plurality of waveguides positioned in an arrayof columns and rows within the probe, each waveguide having an apertureat the working end of the probe which is oriented substantiallyperpendicular to the aperture of the waveguide in any adjacent columnand row of the array, each waveguide constituting an antenna to receivethermo-radiation from tissue opposite the working end of the probe;positioning the probe against a selected area of one of the breasts soas to receive electromagnetic emissions from a plurality ofsubstantially contiguous subcutaneous locations in said one breast;simultaneously detecting said emissions to produce a corresponding firstplurality of electrical signals indicative of the temperatures of saidlocations; digitizing and storing said first plurality of signals;positioning the probe against the corresponding area of the other ofsaid breast so as to receive similar emissions from correspondingsubcutaneous locations in the other breast; simultaneously detectingsaid emissions to produce a corresponding second plurality of electricalsignals indicative of the temperatures at said locations in said otherbreast; digitizing and storing the second plurality of signals, andcomparing the first and second pluralities of signals to determine ifthe detected temperatures from the corresponding locations in thebreasts differ by more than a selected amount.
 4. The method defined inclaim 3 and including the additional step of averaging separately thefirst plurality of signals and the second plurality of signals prior tomaking the temperature comparisons.